1. Field of the Invention
The present invention relates to a method and an apparatus for transmitting acknowledgement channel messages in communication systems.
2. Description of the Related Art
Telecommunication enables transmission of data over a distance for the purpose of communication between a transmitter and a receiver. For wireless communication, the data is usually carried by radio waves and is transmitted using a limited transmission resource. That is, radio waves are transmitted over a period of time using a limited frequency range.
In a contemporary communication system, the information to be transmitted are first encoded and then modulated to generate multiple modulation symbols. The symbols are subsequently mapped into transmission resource. Usually, the transmission resource available for data transmission is segmented into a plurality of equal duration time and frequency slots, so called resource elements. A single resource element or multiple resource elements may be allocated for transmitting the data. When data is transmitted, a control signal may accompany the data to carry information regarding the allocation of the resource elements for the current data transmission. Therefore, when a receiver receives the data and the control signal, the receiver may derive the information regarding resource allocation used for data transmission from the control signal and decodes the received data using the derived information.
During an uplink transmission in the Third (3rd) Generation Partnership Project Long Term Evolution (3GPP LTE) systems, a unit of user equipment (UE) transmits a data packet to a base station (BS) after receiving an uplink scheduling grant (i.e., uplink grant) from the BS. In response to the received data packet from the UE, the BS transmits a downlink acknowledgement channel message (i.e., downlink ACK) to the UE. During a downlink transmission, a BS transmits a data packet to a UE together with or after transmitting a downlink scheduling grant (i.e., downlink grant) to the UE. In response to the received data packet from the BS, the UE transmits an uplink acknowledgement channel message (i.e., uplink ACK) to the UE. An acknowledgement channel message can be either a positive acknowledgement message (ACK) or a negative acknowledgement message (NAK).
Contemporarily, information regarding the allocation of ACK channel resources is transmitted via either explicit signaling or linking to data channel resources. Explicit signaling of ACK channel resource may result in large overhead. Linking ACK channel resources to data channel resources may result in large amount of ACK channel resource requirement, regardless of the actual system load.